Uniquely Strong Electronic Communication between [Mo₂] Units Linked by Dioxolene Dianions

Unprecedented strong electronic communication has been found in dimolybdenum pairs containing quadruply bonded Mo2(DAniF)3+ (DAniF = N,N‘-di-p-anisylformamidinate) units linked by dioxolene (C6X2O42-) anions. The neutral compounds [Mo2(DAniF)3]2(C6X2O4) (1, X = H; 2, X = Cl; 3, X = NO2) and the singly oxidized products {[Mo2(DAniF)3]2(C6X2O4)Mo2}PF6 (4, X = H; 5, X = Cl) have been synthesized and characterized by X-ray crystallography and spectroscopic methods. Unusually short Mo−O distances (∼2.05 Å for 1 and 2, and ∼2.01 Å for 4 and 5) are implicated in the remarkably strong interaction between [Mo2] units via the linkers. This leads to an extensive charge delocalization in the mixed-valence species, which is mediated by the dioxolene linker, as revealed by the large ΔE1/2 values (763, 795, and 816 mV for 1, 2, and 3, respectively). Additional evidence for the strong electronic coupling is provided by UV−vis, NIR, and EPR spectroscopies and DFT calculations.